A waterjet brick in place on a machine
A part being cut on a waterjet brick
The following video shows graphite insulation being cut by a pure waterjet over waterjet brick. Note that there is minimal fixturing needed, because the sideways forces are negligible and the waterjet brick is keeping backsplash from moving the graphite material. The waterjet brick also prevents frosting and marring of the bottom of of the pieces from backsplash.
When cutting small parts, waterjet brick is especially useful as it provides even support for the material and the part doesn’t fall through the slats when it is finished. Slats on most machines are placed one inch (2.5 cm) apart and are designed to support large sheets of material. Although you can use tabs to keep parts attached to a sheet of material, for small parts it can be especially tedious to remove the tabs.
Parts made using a mini-jet nozzle (with smaller kerf) on waterjet brick
The waterjet brick also cuts down on splash back, where the water splashes back onto the part, which can cause frosting on the bottom of a part made from soft materials.
Waterjet brick adds to the cost of making a part and wears out relatively quickly, so you should reserve its use for parts that require it. If you do small parts regularly, you might want to remove the slats in one section of your table and replaced with a piece of waterjet brick. Or, simply place the brick on top of the slats when needed. As with slats, it is possible to get some additional life from brick by flipping it upside down once one side is worn.
Because the waterjet brick is soft plastic, the jet easily cuts into it, meaning that small pieces quickly fill the surface of the catcher tank as they float on top. These do not interfere with machining and they are not toxic, although they make the tank water look ugly. Waterjet brick comes in various colors, and black tends to result in surface material that is not quite as ugly as lighter colors.
Advantages of waterjet brick
- Provides an even surface to work on
- Dense support is good for small parts
- Dense support is good for cutting thin materials
- Soft enough that the jet does not ricochet and mar the underside of your parts
- Typically can be lifted in and placed on top of traditional slats when needed
- Typically can be placed in one section of your tank for use only when needed
- You can use wood screws or similar to fasten material to it for fixturing
- Reduces noise a little when cutting
- Reduces splash outside the tank a little when cutting
Drawbacks to waterjet brick
- Wears out fairly quickly
- Typically not necessary for larger parts unless the material is soft and can be easily marred by splashback from the waterjet
- As it wears, it becomes less useful and parts get stuck in it or it falls apart.
- When the brick is cut, small bits of plastic come loose and turn into a sort of “goo” that floats on top of the water. This goo can plug up small filter openings and you may need to take extra steps to keep this from gumming up your water filtering equipment.
- Wears out even faster if tilting heads are used